Reindex APIedit

Reindex Requestedit

A ReindexRequest can be used to copy documents from one or more indexes into a destination index.

It requires an existing source index and a target index which may or may not exist pre-request. Reindex does not attempt to set up the destination index. It does not copy the settings of the source index. You should set up the destination index prior to running a _reindex action, including setting up mappings, shard counts, replicas, etc.

The simplest form of a ReindexRequest looks like this:

ReindexRequest request = new ReindexRequest(); 
request.setSourceIndices("source1", "source2"); 

Creates the ReindexRequest

Adds a list of sources to copy from

Adds the destination index

The dest element can be configured like the index API to control optimistic concurrency control. Just leaving out versionType (as above) or setting it to internal will cause Elasticsearch to blindly dump documents into the target. Setting versionType to external will cause Elasticsearch to preserve the version from the source, create any documents that are missing, and update any documents that have an older version in the destination index than they do in the source index.


Set the versionType to EXTERNAL

Setting opType to create will cause _reindex to only create missing documents in the target index. All existing documents will cause a version conflict. The default opType is index.


Set the opType to create

By default version conflicts abort the _reindex process but you can just count them instead with:


Set proceed on version conflict

You can limit the documents by adding a query.

request.setSourceQuery(new TermQueryBuilder("user", "kimchy")); 

Only copy documents which have field user set to kimchy



Only copy 10 documents

By default _reindex uses batches of 1000. You can change the batch size with sourceBatchSize.


Use batches of 100 documents

Reindex can also use the ingest feature by specifying a pipeline.


set pipeline to my_pipeline

ReindexRequest also supports a script that modifies the document. It allows you to also change the document’s metadata. The following example illustrates that.

    new Script(
        ScriptType.INLINE, "painless",
        "if (ctx._source.user == 'kimchy') {ctx._source.likes++;}",

setScript to increment the likes field on all documents with user kimchy.

ReindexRequest supports reindexing from a remote Elasticsearch cluster. When using a remote cluster the query should be specified inside the RemoteInfo object and not using setSourceQuery. If both the remote info and the source query are set it results in a validation error during the request. The reason for this is that the remote Elasticsearch may not understand queries built by the modern query builders. The remote cluster support works all the way back to Elasticsearch 0.90 and the query language has changed since then. When reaching older versions, it is safer to write the query by hand in JSON.

    new RemoteInfo(
        "http", remoteHost, remotePort, null,
        new BytesArray(new MatchAllQueryBuilder().toString()),
        user, password, Collections.emptyMap(),
        new TimeValue(100, TimeUnit.MILLISECONDS),
        new TimeValue(100, TimeUnit.SECONDS)

set remote elastic cluster

ReindexRequest also helps in automatically parallelizing using sliced-scroll to slice on _id. Use setSlices to specify the number of slices to use.


set number of slices to use



set scroll time

Optional argumentsedit



Timeout to wait for the reindex request to be performed as a TimeValue


Refresh index after calling reindex

Synchronous executionedit

When executing a ReindexRequest in the following manner, the client waits for the BulkByScrollResponse to be returned before continuing with code execution:

BulkByScrollResponse bulkResponse =
        client.reindex(request, RequestOptions.DEFAULT);



Asynchronous executionedit


client.reindexAsync(request, RequestOptions.DEFAULT, listener); 

The ReindexRequest to execute and the ActionListener to use when the execution completes


A typical listener for reindex looks like:

listener = new ActionListener<BulkByScrollResponse>() {
    public void onResponse(BulkByScrollResponse bulkResponse) {

    public void onFailure(Exception e) {

Called when the execution is successfully completed.

Called when the whole ReindexRequest fails.

Reindex task submissionedit

It is also possible to submit a ReindexRequest and not wait for it completion with the use of Task API. This is an equivalent of a REST request with wait_for_completion flag set to false.

ReindexRequest reindexRequest = new ReindexRequest(); 

TaskSubmissionResponse reindexSubmission = highLevelClient()
    .submitReindexTask(reindexRequest, RequestOptions.DEFAULT); 

String taskId = reindexSubmission.getTask(); 

A ReindexRequest is constructed the same way as for the synchronous method

A submit method returns a TaskSubmissionResponse which contains a task identifier.

The task identifier can be used to get response from a completed task.

Reindex Responseedit

The returned BulkByScrollResponse contains information about the executed operations and allows to iterate over each result as follows:

TimeValue timeTaken = bulkResponse.getTook(); 
boolean timedOut = bulkResponse.isTimedOut(); 
long totalDocs = bulkResponse.getTotal(); 
long updatedDocs = bulkResponse.getUpdated(); 
long createdDocs = bulkResponse.getCreated(); 
long deletedDocs = bulkResponse.getDeleted(); 
long batches = bulkResponse.getBatches(); 
long noops = bulkResponse.getNoops(); 
long versionConflicts = bulkResponse.getVersionConflicts(); 
long bulkRetries = bulkResponse.getBulkRetries(); 
long searchRetries = bulkResponse.getSearchRetries(); 
TimeValue throttledMillis = bulkResponse.getStatus().getThrottled(); 
TimeValue throttledUntilMillis =
List<ScrollableHitSource.SearchFailure> searchFailures =
List<BulkItemResponse.Failure> bulkFailures =

Get total time taken

Check if the request timed out

Get total number of docs processed

Number of docs that were updated

Number of docs that were created

Number of docs that were deleted

Number of batches that were executed

Number of skipped docs

Number of version conflicts

Number of times request had to retry bulk index operations

Number of times request had to retry search operations


Remaining delay of any current throttle sleep or 0 if not sleeping

Failures during search phase

Failures during bulk index operation